Biomedical subjects

Xia Cao

Publications and source records attributed to Xia Cao.

21 records · Page 2Linked to original sources

PubMed2003

Calcium signaling pathway involving calcineurin regulates interleukin-8 gene expression through activation of NF-kappaB in human osteoblast-like cells.

UNLABELLED: Involvement of aberrant IL-8 production by osteoblasts was demonstrated in pathogenesis of inflammatory joint diseases. We thus investigated intracellular signaling pathways leading to IL-8 expression in human osteoblast-like HOS-TE85 cells. It was demonstrated that Ca2+ signaling pathway involving calcineurin regulates IL-8 gene expression through activation of a transcription factor, NF-kappaB. INTRODUCTION: Involvement of aberrant interleukin (IL)-8 production by osteoblasts was demonstrated in pathogenesis of inflammatory joint diseases. However, intracellular signaling pathways leading to IL-8 expression in osteoblasts have been poorly explored. Because a variety of external stimuli was shown to increase intracellular Ca2+ in osteoblasts, we investigated effects of Ca(2+)-ionophore and phorbol-myristate-acetate (Ion/PMA) on IL-8 expression in human osteoblast-like HOS-TE85 cells and compared the effects with those elicited by TNF-alpha. MATERIALS AND METHODS: HOS-TE85 cells were treated with Ion/PMA or TNF-alpha in the presence and absence of calcineurin inhibitors (CnI), cyclosporin A, and FK506. IL-8 mRNA levels and its promoter activities were examined by Northern blot and luciferase reporter analyses, respectively. Electrophoretic mobility shift assay (EMSA) was used to evaluate DNA binding activities of transcription factors such as NF-kappaB. Degradation of IkappaB, a cytoplasmic NF-kappaB-inhibitory protein, was examined by Western blot analysis. RESULTS: Ion/PMA and TNF-alpha induced IL-8 mRNA expression. Interestingly, CnI attenuated the induction by Ion/PMA, but not that by TNF-alpha. Promoter activity was also increased by both stimuli, and only the Ion/PMA-dependent increase was suppressed by CnI. Introduction of mutations in the promoter demonstrated that one NF-kappaB site was responsible for the suppression by CnI. EMSA revealed that this site binds with NF-kappaB containing p65 that was activated by Ion/PMA and TNF-alpha and that CnI inhibited only Ion/PMA-dependent NF-kappaB activation. Accordingly, CnI blocked only Ion/PMA-dependent degradation of IkappaB-alpha. In addition, the basal and Ion/PMA-dependent IL-8 promoter activities were enhanced by co-transfection of constitutively active calcineurin. CONCLUSION: These results show that the Ca2+ signaling pathway involving calcineurin regulates IL-8 gene expression through activation of NF-kappaB in human osteoblast-like cells.

Antineoplastic Agents↗

PubMed2002

Novel human ZAKI-4 isoforms: hormonal and tissue-specific regulation and function as calcineurin inhibitors.

We identified a thyroid hormone [3,5,3'-tri-iodothyronine (T(3))]-responsive gene, ZAKI-4, in cultured human skin fibroblasts. It belongs to a family of genes that encode proteins containing a conserved motif. The motif binds to calcineurin and inhibits its phosphatase activity. In the present study, we have demonstrated three different ZAKI-4 transcripts, alpha, beta1 and beta2, in human brain by 5'- and 3'-RACE (rapid amplification of cDNA ends). The alpha transcript was identical with the one that we originally cloned from human fibroblasts and the other two are novel. The three transcripts are generated by alternative initiation and splicing from a single gene on the short arm of chromosome 6. It is predicted that beta1 and beta2 encode an identical protein product, beta, which differs from alpha in its N-terminus. Since alpha and beta contain an identical C-terminal region harbouring the conserved motif, both isoforms are suggested to inhibit calcineurin activity. Indeed, each isoform associates with calcineurin A and inhibits its activity in a similar manner, suggesting that the difference in N-terminus of each isoform does not affect the inhibitory function on calcineurin. An examination of the expression profile of the three transcripts in 12 human tissues revealed that the alpha transcript is expressed exclusively in the brain, whereas beta transcripts are expressed ubiquitously, most abundantly in brain, heart, skeletal muscle and kidney. It was also demonstrated that human skin fibroblasts express both alpha and beta transcripts, raising the question of which transcript is up-regulated by T(3). It was revealed that T(3) markedly induced the expression of alpha isoform but not of beta. This T(3)-mediated increase in the alpha isoform was associated with a significant decrease in endogenous calcineurin activity. These results suggest that the expression of ZAKI-4 isoforms is subjected to distinct hormonal as well as tissue-specific regulation, constituting a complex signalling network through inhibition of calcineurin.

Alternative Splicing↗

PubMed2002

Oxidoreductive modification of two cysteine residues in paired domain by Ref-1 regulates DNA-binding activity of Pax-8.

We have reported reversible oxidoreductive regulation of DNA-binding activity of Pax-8: oxidation inhibits its binding and subsequent reduction restores the binding. Here, we show that Cys-45 and Cys-57 in the paired domain of rat Pax-8, which are conserved in all Pax members, are responsible for the redox regulation of its binding. Electrophoretic mobility shift assay using deletion mutants and mutants with substitution of cysteine with serine revealed that oxidation by diamide of either Cys-45 or Cys-57 loses the DNA binding of Pax-8. An intracellular oxidoreductive enzyme redox factor-1 (Ref-1) could reduce the oxidized Cys-45 or Cys-57 and restored the binding. Furthermore, reporter gene assay showed that transcriptional activity of wild-type Pax-8 was enhanced by co-expression of Ref-1. When the mutant with double substitutions of Cys-45 and Cys-57, which was insensitive to oxidation, was transfected, the basal transactivation level was much higher than that of wild-type Pax-8, while it was not enhanced by Ref-1. These results demonstrated that oxidoreductive modification of Cys-45 and Cys-57 via Ref-1 plays a role in redox regulation of Pax-8 in living cells.

Animals↗